Journal of Ultrasound in Medicine, Vol 8, Issue 1 7-13, Copyright © 1989 by American Institute of Ultrasound in Medicine
Correlation of experimental rCBF determinations in goats with flow measurements from a Doppler-modified carotid artery shunt
C. M. Loftus, J. A. Silvidi, J. A. Becker, B. V. Miller and D. D. Bernstein
Division of Neurosurgery, College of Medicine, University of Iowa.
A carotid artery shunt system has been developed that continuously monitors
blood flow rates by embedding a Doppler crystal in the shunt wall. The
crystal ranges through a "liquid lens" that enables it to be placed without
violation of the shunt lumen. Because the crystal is at a fixed angle (45
degrees) to the axis of blood flow and the diameter of the lumen remains
constant, a linear relationship exists between flow rates and the Doppler
velocity signal. This shunt system was previously tested in vitro using a
pulsatile pump and was found to be accurate to within 4.7% of the actual
flow rate. In the present study, animal (goat) experiments were performed
consisting of simultaneous carotid shunt flow and bilateral rCBF
measurements by the radiolabeled microsphere technique to determine in vivo
the accuracy of this Doppler modified shunt and to ascertain the ability of
shunt flow to increase in the face of acute contralateral carotid
occlusion. Data from five animals show that in vivo shunt flow can be
recorded to within 13% of control rCBF and that shunt flow increases nearly
50% under conditions of distal demand (contralateral carotid occlusion).
This device may prove useful in laboratory studies of carotid shunt
dynamics and in clinical practice to quickly detect correctable shunt flow
abnormalities.
